PET Assays of Striatal Dopamine Marker in Cocaine Craving

Background: * Cues related to past drug use induce a particular pattern of brain activation, which has been correlated with craving for cocaine in active cocaine abusers. Researchers are interested in determining the role of the brain chemical dopamine in cue-elicited as well as spontaneous craving for cocaine. * To study the role of dopamine in cocaine craving, researchers will use positron emission tomography (PET) to compare the neural reactions of cocaine users with those of non-substance-abusing healthy volunteers. Researchers hope that the data gathered from this study will lead to the development of more effective anti-craving medications. Objectives: * To clarify the role of dopamine in cue-elicited responses that contribute to cocaine abuse. * To determine if PET results of this study differ with various means of administering PET chemicals. Eligibility: \- Individuals 21 to 44 years of age who are either current cocaine users (at least twice per week) or healthy volunteers without a history of drug abuse. Design: * Cocaine-using participants will enter the inpatient clinical research ward at the National Institute on Drug Abuse (NIDA) Addiction Research Center for 2 nights before the day of the study. In addition, these participants will stay overnight at NIDA the evening after each PET session and will be discharged the following day. Cocaine-using participants will be required to perform a balance test before the study to provide a baseline response in case they require anti-anxiety medications to cope with the effects of the study. * Control subjects will not be required to stay overnight and will arrive as outpatients for the PET session. All participants will be required to abstain from alcohol and caffeine consumption from midnight before each study session, and will not be permitted to smoke on the day of testing. * \- On the day of the study, participants will undergo a practice session to set up the PET scanning equipment. Following the practice session, participants will be shown video recordings of images that are related to nature (e.g., seashells) or to drug abuse (e.g., drug paraphernalia). Participant reactions will be studied through the PET monitoring, and the study will be conducted in two separate PET sessions with a break in between. Individuals in the cocaine-using group may receive anti-anxiety medication if the stimulus cues increase anxiety related to cocaine craving. * Different groups of participants will receive different methods of PET chemical administration, and researchers will compare these methods.